CHAPTER III. 



CLASSIFICATION OF PLANTS. PROTOPHYTES. 



FOR the sake of convenience it is desirable to collect into 

 groups such plants as are evidently related; but as our knowl- 

 edge of many forms is still very imperfect, any classification 

 we may adopt must be to a great extent only provisional, and 

 subject to change at any time, as new forms are discovered or 

 others become better understood. 



The following general divisions are usually accepted : I. 

 Sub-kingdom (or Branch) ; II. Class ; III. Order ; IV. Family ; 

 V. Genus; VI. Species. 



To illustrate : The white pine belongs to the highest great 

 division (sub-kingdom) of the plant kingdom. The plants of 

 this division all produce seeds, and hence are called " sperma- 

 phytes" ("seed plants"). They may be divided into two 

 groups (classes), distinguished by certain peculiarities in the 

 flowers and seeds. These are named respectively "gymno- 

 sperms " and " angiosperms," and to the first our plant belongs. 

 The gymnosperms may be further divided into several subor- 

 dinate groups (orders), one of which, the CQnifers, or cone-bear- 

 ing evergreens, includes our plant. This order includes several 

 families, among them the fir family (Abietinece), including the 

 pines and firs. Of the sub-divisions (genera, sing, genus) of 

 the fir family, one of the most familiar is the genus Pinus, 

 which embraces all the true pines. Comparing different kinds 

 of pines, we find that they differ in the form of the cones, ar- 

 rangement of the leaves, and other minor particulars. The form 

 we have selected differs from all other native forms in its cones, 

 and also in having the leaves in fives, instead of twos or threes, 

 as in most other kinds. Therefore to distinguish the white pine 

 from all other pines, it is given a " specific " name, strobus. 



